I own a 1991 Honda Accord SE and experiencing this strange problem and hoping I can get some input or possible remedy. I have this flashing "S" on my instrument panel and the speedometer stays on "0" MPH reading at any speed when it happens, then eventually the check engine light follows. Generally, the car starts off normal and this problem only occurs sporadically. Normally the "S" is steady solid when I engaged the sports option on my automatic shifter but in this case, engaged or not, I get the flashing "S". I recently added a security alarm on this vehicle, professionaly installed, and soon after I started getting this problem. I don't know if it's related or it happened by coincidence. I don't think the installer can screw up my instrument panel during the wiring installations, or is that possible? I'm reaching out to anyone out there with Honda expertise to give me a hand. I appreciate any input or suggestions.